Fix: hash table growth (for small tables) should be limited (v2)

[lttng-tools.git] / src / common / hashtable / rculfhash.c

diff --git a/src/common/hashtable/rculfhash.c b/src/common/hashtable/rculfhash.c
index b430a3dec76e681ebf561f33bb9fcc767c713037..ebdc4ffaa8ee84842eb18c4c0588042fade9c66c 100644 (file)
--- a/src/common/hashtable/rculfhash.c
+++ b/src/common/hashtable/rculfhash.c
@@ -726,9 +726,32 @@ void check_resize(struct cds_lfht *ht, unsigned long size, uint32_t chain_len)
        if (chain_len > 100)
                dbg_printf("WARNING: large chain length: %u.\n",
                           chain_len);
-       if (chain_len >= CHAIN_LEN_RESIZE_THRESHOLD)
-               cds_lfht_resize_lazy_grow(ht, size,
-                       cds_lfht_get_count_order_u32(chain_len - (CHAIN_LEN_TARGET - 1)));
+       if (chain_len >= CHAIN_LEN_RESIZE_THRESHOLD) {
+               int growth;
+
+               /*
+                * Ideal growth calculated based on chain length.
+                */
+               growth = cds_lfht_get_count_order_u32(chain_len
+                               - (CHAIN_LEN_TARGET - 1));
+               if ((ht->flags & CDS_LFHT_ACCOUNTING)
+                               && (size << growth) >= (1UL << COUNT_COMMIT_ORDER)) {
+                       /*
+                        * If ideal growth expands the hash table size
+                        * beyond the "small hash table" sizes, use the
+                        * maximum small hash table size to attempt
+                        * expanding the hash table. This only applies
+                        * when node accounting is available, otherwise
+                        * the chain length is used to expand the hash
+                        * table in every case.
+                        */
+                       growth = COUNT_COMMIT_ORDER -
+                               cds_lfht_get_count_order_u32(size);
+                       if (growth <= 0)
+                               return;
+               }
+               cds_lfht_resize_lazy_grow(ht, size, growth);
+       }
 }
 
 static